Raw model output on the native 0.25° grid — no MOS, no bias correction, no post-processing. Scores understate operational forecast quality. Read the fairness statement →

CastCheck methodology v0.2 · data through 2026-08-30

Seattle-Tacoma · NCEP GFS · lead day 3

KSEA · gfs · lead 3

Target day = initialization date + 3 days. This page is a permanent link: the numbers change as history accumulates, the address and the methodology version do not.

Scores use the latest model version segment, gfs-0p25, starting 2026-08-01 — days before that ran a different version of the model and are excluded rather than silently pooled. Of the scored days, 1 carry a QC flag on the observation.

JSON for this page CSV of the daily errors Cite this page

Every number for this combination

All four windows × both initializations × both interpolations × both variables. Errors are computed in °C and shown in °F; CI is a 95 % moving-block bootstrap interval. MAE debiased and skill, debiased remove the constant offset of the window first, so a station that the model always reads a degree too warm is not scored as if it had no skill — compare the two skill columns to see how much of the error is a fixed offset. n QC next to n counts days whose observation carries a QC flag.

VariableInitMethod Windown MAE °F MAE debiased Bias °F RMSE °F ±1 °F±2 °F±3 °F Skill Skill, debiased Period
tmax00Zbilinear30d27 1 QC4.61 [3.67, 5.63]3.35+3.20 [0.84, 5.47]5.36 [4.14, 6.42]7% [0%, 20%]15%33%+0.27+0.472026-08-04 → 2026-08-30
tmax00Zbilinear90d27 1 QC4.61 [3.58, 5.62]3.35+3.20 [0.41, 5.47]5.36 [3.98, 6.38]7% [0%, 22%]15%33%+0.27+0.472026-08-04 → 2026-08-30
tmax00Zbilinear365d27 1 QC4.61 [3.44, 5.71]3.35+3.20 [0.15, 5.67]5.36 [3.94, 6.47]7% [0%, 22%]15%33%+0.27+0.472026-08-04 → 2026-08-30
tmax00Zbilinearall27 1 QC4.61 [3.51, 5.64]3.35+3.20 [0.34, 5.60]5.36 [4.04, 6.44]7% [0%, 21%]15%33%+0.27+0.472026-08-04 → 2026-08-30
tmax00Znearest30d27 1 QC4.48 [3.65, 5.41]3.40+2.87 [0.45, 5.12]5.18 [4.05, 6.25]4% [0%, 11%]19%37%+0.29+0.462026-08-04 → 2026-08-30
tmax00Znearest90d27 1 QC4.48 [3.49, 5.37]3.40+2.87 [0.00, 5.08]5.18 [3.91, 6.17]4% [0%, 11%]19%37%+0.29+0.462026-08-04 → 2026-08-30
tmax00Znearest365d27 1 QC4.48 [3.46, 5.46]3.40+2.87 [-0.12, 5.32]5.18 [3.87, 6.28]4% [0%, 11%]19%37%+0.29+0.462026-08-04 → 2026-08-30
tmax00Znearestall27 1 QC4.48 [3.52, 5.41]3.40+2.87 [-0.07, 5.28]5.18 [3.90, 6.23]4% [0%, 11%]19%37%+0.29+0.462026-08-04 → 2026-08-30
tmax12Zbilinear30d27 1 QC4.71 [3.57, 5.88]3.36+3.51 [1.47, 5.56]5.57 [4.21, 6.86]19% [7%, 31%]19%22%+0.26+0.472026-08-04 → 2026-08-30
tmax12Zbilinear90d27 1 QC4.71 [3.51, 5.79]3.36+3.51 [1.08, 5.53]5.57 [4.14, 6.84]19% [5%, 33%]19%22%+0.26+0.472026-08-04 → 2026-08-30
tmax12Zbilinear365d27 1 QC4.71 [3.30, 5.93]3.36+3.51 [0.85, 5.70]5.57 [3.84, 6.91]19% [6%, 35%]19%22%+0.26+0.472026-08-04 → 2026-08-30
tmax12Zbilinearall27 1 QC4.71 [3.35, 5.88]3.36+3.51 [0.88, 5.71]5.57 [3.98, 6.85]19% [5%, 36%]19%22%+0.26+0.472026-08-04 → 2026-08-30
tmax12Znearest30d27 1 QC4.48 [3.41, 5.59]3.24+3.32 [1.33, 5.33]5.33 [3.98, 6.66]15% [7%, 23%]19%30%+0.29+0.492026-08-04 → 2026-08-30
tmax12Znearest90d27 1 QC4.48 [3.37, 5.51]3.24+3.32 [1.05, 5.22]5.33 [3.91, 6.60]15% [5%, 25%]19%30%+0.29+0.492026-08-04 → 2026-08-30
tmax12Znearest365d27 1 QC4.48 [3.17, 5.58]3.24+3.32 [0.76, 5.44]5.33 [3.64, 6.69]15% [5%, 26%]19%30%+0.29+0.492026-08-04 → 2026-08-30
tmax12Znearestall27 1 QC4.48 [3.26, 5.54]3.24+3.32 [0.76, 5.42]5.33 [3.76, 6.63]15% [5%, 26%]19%30%+0.29+0.492026-08-04 → 2026-08-30
tmin00Zbilinear30d27 1 QC1.65 [1.28, 2.04]1.64-0.50 [-1.43, 0.33]2.18 [1.65, 2.65]41% [29%, 53%]67%81%+0.28+0.292026-08-04 → 2026-08-30
tmin00Zbilinear90d27 1 QC1.65 [1.25, 2.09]1.64-0.50 [-1.63, 0.42]2.18 [1.60, 2.70]41% [27%, 53%]67%81%+0.28+0.292026-08-04 → 2026-08-30
tmin00Zbilinear365d27 1 QC1.65 [1.23, 2.14]1.64-0.50 [-1.56, 0.42]2.18 [1.60, 2.72]41% [27%, 55%]67%81%+0.28+0.292026-08-04 → 2026-08-30
tmin00Zbilinearall27 1 QC1.65 [1.20, 2.13]1.64-0.50 [-1.69, 0.44]2.18 [1.59, 2.71]41% [28%, 55%]67%81%+0.28+0.292026-08-04 → 2026-08-30
tmin00Znearest30d27 1 QC1.83 [1.31, 2.36]1.66+1.13 [0.05, 1.98]2.38 [1.62, 3.07]37% [22%, 54%]56%85%+0.20+0.282026-08-04 → 2026-08-30
tmin00Znearest90d27 1 QC1.83 [1.23, 2.39]1.66+1.13 [-0.20, 2.08]2.38 [1.49, 3.08]37% [20%, 55%]56%85%+0.20+0.282026-08-04 → 2026-08-30
tmin00Znearest365d27 1 QC1.83 [1.18, 2.38]1.66+1.13 [-0.20, 2.09]2.38 [1.42, 3.06]37% [20%, 57%]56%85%+0.20+0.282026-08-04 → 2026-08-30
tmin00Znearestall27 1 QC1.83 [1.18, 2.39]1.66+1.13 [-0.30, 2.10]2.38 [1.44, 3.08]37% [20%, 57%]56%85%+0.20+0.282026-08-04 → 2026-08-30
tmin12Zbilinear30d27 1 QC1.54 [1.05, 2.06]1.41-0.88 [-1.88, -0.02]2.02 [1.50, 2.49]48% [26%, 70%]67%85%+0.33+0.392026-08-04 → 2026-08-30
tmin12Zbilinear90d27 1 QC1.54 [1.01, 2.15]1.41-0.88 [-2.13, 0.02]2.02 [1.41, 2.57]48% [25%, 71%]67%85%+0.33+0.392026-08-04 → 2026-08-30
tmin12Zbilinear365d27 1 QC1.54 [0.95, 2.18]1.41-0.88 [-2.17, 0.10]2.02 [1.37, 2.57]48% [22%, 73%]67%85%+0.33+0.392026-08-04 → 2026-08-30
tmin12Zbilinearall27 1 QC1.54 [0.98, 2.21]1.41-0.88 [-2.21, 0.05]2.02 [1.38, 2.60]48% [25%, 73%]67%85%+0.33+0.392026-08-04 → 2026-08-30
tmin12Znearest30d27 1 QC1.65 [1.24, 2.08]1.58+0.78 [-0.40, 1.74]2.06 [1.51, 2.61]30% [19%, 43%]63%89%+0.28+0.312026-08-04 → 2026-08-30
tmin12Znearest90d27 1 QC1.65 [1.18, 2.09]1.58+0.78 [-0.74, 1.78]2.06 [1.48, 2.61]30% [15%, 50%]63%89%+0.28+0.312026-08-04 → 2026-08-30
tmin12Znearest365d27 1 QC1.65 [1.16, 2.13]1.58+0.78 [-0.77, 1.90]2.06 [1.44, 2.68]30% [16%, 50%]63%89%+0.28+0.312026-08-04 → 2026-08-30
tmin12Znearestall27 1 QC1.65 [1.13, 2.10]1.58+0.78 [-0.79, 1.81]2.06 [1.41, 2.62]30% [14%, 50%]63%89%+0.28+0.312026-08-04 → 2026-08-30

+ model too warm · − model too cold · bias interval includes zero · ★ lowest MAE · = not distinguishable from the leader · ▼ significantly worse · n < 30 greyed and unranked · CI is a 95 % moving-block bootstrap interval.

Daily error, last 90 days

Daily forecast minus observed error in °F for NCEP GFS at KSEA, lead day 3, 00Z bilinear tmax+20+100-10-202026-08-04: +5.16 °F2026-08-05: +3.74 °F2026-08-06: +5.44 °F2026-08-07: +1.52 °F2026-08-08: +3.95 °F2026-08-09: +7.56 °F2026-08-10: +10.55 °F2026-08-11: +3.17 °F2026-08-12: +3.07 °F2026-08-13: +2.88 °F2026-08-14: +8.51 °F2026-08-15: +9.42 °F2026-08-16: +9.13 °F2026-08-17: +6.27 °F2026-08-18: +2.79 °F2026-08-19: -0.36 °F2026-08-20: -0.84 °F2026-08-21: +5.37 °F2026-08-22: -5.97 °F2026-08-23: -1.27 °F2026-08-24: -3.85 °F2026-08-25: +8.01 °F2026-08-26: +3.65 °F2026-08-27: +2.27 °F2026-08-28: +3 °F2026-08-29: -2.32 °F2026-08-30: -4.52 °F2026-08-042026-08-30°F, forecast − observed
Forecast − observed, °F, 00Z bilinear daily maximum. The dashed line is zero; the thick line is a centred 7-day mean, drawn only where the whole window is present. Gaps are days with no score, never interpolation. Hover a point for its date and value.
The same series as a table (27 days, newest first) · download CSV
Climatological dayError °F
2026-08-30-4.52
2026-08-29-2.32
2026-08-28+3.00
2026-08-27+2.27
2026-08-26+3.65
2026-08-25+8.01
2026-08-24-3.85
2026-08-23-1.27
2026-08-22-5.97
2026-08-21+5.37
2026-08-20-0.84
2026-08-19-0.36
2026-08-18+2.79
2026-08-17+6.27
2026-08-16+9.13
2026-08-15+9.42
2026-08-14+8.51
2026-08-13+2.88
2026-08-12+3.07
2026-08-11+3.17
2026-08-10+10.55
2026-08-09+7.56
2026-08-08+3.95
2026-08-07+1.52
2026-08-06+5.44
2026-08-05+3.74
2026-08-04+5.16

Error distribution

Distribution of the signed daily error in °F for NCEP GFS at KSEA, lead day 3-20 to -18 °F: 0 days-18 to -16 °F: 0 days-16 to -14 °F: 0 days-14 to -12 °F: 0 days-12 to -10 °F: 0 days-10 to -8 °F: 0 days-8 to -6 °F: 0 days-6 to -4 °F: 2 days-4 to -2 °F: 2 days-2 to 0 °F: 3 days0 to 2 °F: 1 day2 to 4 °F: 9 days4 to 6 °F: 3 days6 to 8 °F: 2 days8 to 10 °F: 4 days10 to 12 °F: 1 day12 to 14 °F: 0 days14 to 16 °F: 0 days16 to 18 °F: 0 days18 to 20 °F: 0 daysdashed: P50 |e| 3.85 · P90 |e| 8.76 °F-200+20 °Fn = 27 days
All scored days for 00Z bilinear daily maximum, 20 equal bins. The dashed marks are the 50th and 90th percentiles of the absolute error, mirrored on both sides. Hover a bar for its bin and count.
Bin counts as a table
From °FTo °FDays
-20.00-18.000
-18.00-16.000
-16.00-14.000
-14.00-12.000
-12.00-10.000
-10.00-8.000
-8.00-6.000
-6.00-4.002
-4.00-2.002
-2.00+0.003
+0.00+2.001
+2.00+4.009
+4.00+6.003
+6.00+8.002
+8.00+10.004
+10.00+12.001
+12.00+14.000
+14.00+16.000
+16.00+18.000
+18.00+20.000

Month by month

00Z bilinear daily maximum, newest first.

Monthn MAE °FBias °F
2026-08274.61 +3.20

Availability

ModelScored period DaysCoverage
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27
NCEP GFS2026-08-04 → 2026-08-30 27

Compared with other models

Paired bootstrap on the days both models cover (90d, 00Z, bilinear, daily maximum). Negative means NCEP GFS has the lower MAE. "Distinguishable" means the 95 % interval excludes zero.

Other modelCommon days MAE difference °FDistinguishable
ECMWF AIFS Single 27 -0.53 [-3.10, 1.68] no
GraphCast (IFS init) 25 +0.16 [-2.29, 2.21] no
ECMWF IFS HRES 22 +1.82 [0.61, 3.23] yes
Persistence (baseline) 27 -1.72 [-4.63, 0.34] no

Cite this page

ShortCastCheck, KSEA gfs lead 3, methodology v0.2, accessed 2026-08-31, https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/3/

LongCastCheck (2026). Station-level verification of raw weather-model 2 m temperature forecasts: KSEA (Seattle-Tacoma), model gfs, lead day 3. Methodology version 0.2, schema version 0.1, data through 2026-08-30. Accessed 2026-08-31. https://castcheck.zifanzhang.com/station/KSEA/model/gfs/lead/3/

Accessed2026-08-31 (data through 2026-08-30; page built 2026-08-31T03:52:06+00:00)

JSON CSV all scores methodology v0.2 licence